US9964706B2 - Structure of an input end of an optical fiber - Google Patents

Structure of an input end of an optical fiber Download PDF

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US9964706B2
US9964706B2 US15/127,281 US201615127281A US9964706B2 US 9964706 B2 US9964706 B2 US 9964706B2 US 201615127281 A US201615127281 A US 201615127281A US 9964706 B2 US9964706 B2 US 9964706B2
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optical fiber
cladding
fiber
diameter
core
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US20180045888A1 (en
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Xiaoguang He
Kuiyan SONG
Lei Xu
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BWT Beijing Ltd
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BWT Beijing Ltd
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/36—Mechanical coupling means
    • G02B6/38—Mechanical coupling means having fibre to fibre mating means
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/36—Mechanical coupling means
    • G02B6/38—Mechanical coupling means having fibre to fibre mating means
    • G02B6/3807—Dismountable connectors, i.e. comprising plugs
    • G02B6/381—Dismountable connectors, i.e. comprising plugs of the ferrule type, e.g. fibre ends embedded in ferrules, connecting a pair of fibres
    • G02B6/3813—Dismountable connectors, i.e. comprising plugs of the ferrule type, e.g. fibre ends embedded in ferrules, connecting a pair of fibres for transmission of high energy beam
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/01205—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
    • C03B37/01211—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments by inserting one or more rods or tubes into a tube
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02052—Optical fibres with cladding with or without a coating comprising optical elements other than gratings, e.g. filters
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/262—Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06708—Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
    • H01S3/06716—Fibre compositions or doping with active elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/0675—Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers

Definitions

  • the present invention relates to the field of laser technology, particularly to a structure of an input end of an optical fiber.
  • a high-power laser When a high-power laser is coupled into an optical fiber, if the size of the light spot of the incident light is larger than the diameter of the core of the optical fiber or the incident angle exceeds the numerical aperture angle of the optical fiber, a portion of light will enter the cladding of the optical fiber.
  • the cladding light could damage the fiber tip if it leaks at the incident end, or burn the fiber if the cladding light is absorbed by the buffer layer when travelling along the fiber.
  • FIG. 1 shows a structure of an input end of the optical fiber disclosed in US 20100195957A1.
  • the optical fiber is protected by a transparent sleeve outside.
  • Either the surface of the optical fiber is pretreated to be rough, or materials with refractive index equal to or greater than that of the fiber cladding are used to fill the gap between the sleeve and fiber.
  • the refractive index of the transparent sleeve is equal to or greater than that of the cladding
  • the outer surface of the sleeve is processed to rough
  • the length of the sleeve is long enough so that the residual light in the cladding, before reaching the end of the connector, can leak out of the optical fiber.
  • This invention allows the light to escape from the connector without generating heat, which avoids the thermal damage to the connector.
  • FIG. 2 shows another structure of an input end of the optical fiber disclosed in US 20120262938A1.
  • the core extension can be formed by removing a length of cladding from the fiber by etching or other processes.
  • a certain thickness of the cladding can also be left on the core extension, where, for example, the thickness is smaller than 1 ⁇ 3, 1 ⁇ 5, 1/10, 1/20 or 1/100 of that of the cladding.
  • etching is needed to remove the cladding
  • etching process causes the optical fiber to be fragile, which reduces the long-term reliability of the fiber, and the optical fiber after etching is too weak to go through cutting, grinding and other processes.
  • the end face should also be modified by roughening, being coated with a reflective film or other processes, which is very difficult.
  • the present invention provides a structure of an input end of an optical fiber, which can solve the problems in prior arts or at least partially solve those problems.
  • the structure of the input end of the optical fiber comprises a first optical fiber and a second optical fiber
  • first optical fiber and the second optical fiber are coaxial, one end of the first optical fiber is used to receive optical beam, and the other end of the first fiber is engaged with the second optical fiber;
  • first optical fiber comprise a fiber core and a first cladding surrounding its fiber core
  • second optical fiber comprise a fiber core and a first cladding surrounding its fiber core
  • a diameter of the first cladding of the first optical fiber is larger than a diameter of the first cladding of the second optical fiber and a difference between them is larger than a first preset threshold
  • a diameter of the fiber core of the first optical fiber is smaller than or equal to a diameter of the fiber core of the second optical fiber and a difference between them is smaller than a second preset threshold.
  • the structure of the input end of the optical fiber further comprises a second cladding of the first optical fiber surrounding the first cladding of the first optical fiber.
  • the diameter of the first cladding of the first optical fiber gradually and uniformly decreases from a preset position until the engagement of the first optical fiber and the second optical fiber.
  • the structure of the input end of the optical fiber further comprises an end cap
  • a material of the end cap is quartz or glass, and a diameter of the end cap is larger than the diameter of the fiber core of the first optical fiber.
  • the structure of the input end of the optical fiber further comprises a sleeve
  • the sleeve surrounds the first optical fiber and the second optical fiber, and a material of the sleeve is metal or glass;
  • the gap formed between the inner surface of the sleeve and the outer surface of the first cladding of the second optical fiber is filled with glue, or the inner surface of the sleeve and the outer surface of the first cladding of the second optical fiber are welded by laser or electric arc.
  • an end face of the one end of the first optical fiber is coated with an antireflection film.
  • the other end of the first optical fiber is engaged with the second optical fiber by way of electrode discharge fusion, laser heating fusion or adhesive bonding.
  • a ratio of the diameter of the first cladding of the first optical fiber to the diameter of the fiber core of the first optical fiber is 1.1 ⁇ 50;
  • a difference of the diameter of the fiber core of the first optical fiber and the diameter of the fiber core of the second optical fiber is 2 times coaxial precision of the first optical fiber and the second optical fiber.
  • a length of the first optical fiber is 1 mm ⁇ 3000 mm.
  • the first optical fiber is a single-mode optical fiber or a multimode optical fiber
  • the second optical fiber is a single-mode optical fiber or a multimode optical fiber
  • the first optical fiber is a shaped optical fiber with D-shaped or square shaped fiber core and cladding, or the first optical fiber is a photonic crystal optical fiber;
  • the second optical fiber is a shaped optical fiber with D-shaped or square shaped fiber core and cladding, or the second optical fiber is a photonic crystal optical fiber.
  • a length of optical fiber with a larger diameter is engaged at the front end of the optical fiber.
  • the structure of the input end of the optical fiber has advantages such as simple structure, easy for implementation, high reliability. And it can efficiently prevent light from entering the cladding of the optical fiber so as to prevent light from converting into heat, thus avoiding thermal damage to the optical fiber.
  • FIG. 1 is a schematic diagram showing a conventional structure of an input end of an optical fiber
  • FIG. 2 is a schematic diagram showing another conventional structure of an input end of an optical fiber
  • FIG. 3 is a schematic diagram showing a structure of an input end of an optical fiber according to Embodiment 1 of the present invention.
  • FIG. 4A is a schematic diagram showing an optical path in which an incident light enters the structure of the input end of the optical fiber according to one embodiment of the present invention
  • FIG. 4B is a schematic diagram showing an optical path in which an incident light enters the structure of the input end of the optical fiber according to another embodiment of the present invention.
  • FIG. 5 is a schematic diagram showing a structure of an input end of an optical fiber according to Embodiment 2 of the present invention:
  • FIG. 6 is a schematic diagram showing a structure of an input end of an optical fiber according to Embodiment 3 of the present invention.
  • FIG. 7 is a schematic diagram showing a structure of an input end of an optical fiber according to Embodiment 4 of the present invention.
  • FIG. 8 is a schematic diagram showing a structure of an input end of an optical fiber according to Embodiment 5 of the present invention.
  • FIG. 3 is a schematic diagram showing a structure of an input end of an optical fiber according to Embodiment 1 of the present invention.
  • the structure of the input end of the optical fiber comprises a first optical fiber 1 and a second optical fiber 2 ; the first optical fiber 1 and the second optical fiber 2 are coaxial, one end of the first optical fiber 1 is used to receive light beam, and the other end of the first optical fiber 1 is engaged with the second optical fiber.
  • the first optical fiber 1 comprises a fiber core and a first cladding surrounding its fiber core;
  • the second optical fiber 2 comprises a fiber core and a first cladding surrounding its fiber core.
  • a diameter ⁇ 1 of the first cladding of the first optical fiber is larger than a diameter ⁇ 4 of the first cladding of the second optical fiber, and a difference between them is larger than a first preset threshold;
  • a diameter ⁇ 2 of the fiber core of the first optical fiber is smaller than or equal to a diameter ⁇ 3 of the fiber core of the second optical fiber, and a difference between them is smaller than a second preset threshold.
  • the diameter of the first cladding of the first optical fiber is larger than the diameter of the first cladding of the second optical fiber, so that most of lights entering the first cladding of the first optical fiber leak out of the first optical fiber and the second optical fiber and into outer space at the engagement of the first optical fiber and the second optical fiber, and only minor of the light enters the first cladding of the second optical fiber, which improves security of the structure of the input end of the optical fiber.
  • both the first optical fiber 1 and the second optical fiber 2 are a multimode optical fiber, and the other end of the first optical fiber 1 is engaged with the second optical fiber 2 by way of electrode discharge fusion, laser heating fusion or adhesive bonding.
  • a ratio ⁇ 1 / ⁇ 2 of the diameter ⁇ 1 of the first cladding of the first optical fiber to the diameter ⁇ 2 of the fiber core of the first optical fiber is 1.1 ⁇ 50; the diameter ⁇ 2 of the fiber core of the first optical fiber is smaller than or equal to the diameter ⁇ 3 of the fiber core of the second optical fiber.
  • a length L 1 of the first optical fiber 1 should be larger than 1 mm.
  • the length L 1 of the first optical fiber 1 can be selected from a range of 1 mm ⁇ 3000 mm.
  • the outer surface of the first optical fiber 1 can be processed by roughening so as to make light in the first cladding of the first optical fiber scatter out of the lateral surface of the optical fiber.
  • the first optical fiber 1 is cut into a length L 1 after engaging the first optical fiber 1 with the second optical fiber 2 , and then to process the end face of the first optical fiber 1 by grinding, polishing and so on and coating with an antireflection film; alternatively it is also possible to prepare a length L 1 of the first optical fiber 1 firstly, and then processing an end face of the first optical fiber 1 by grinding, polishing and so on and coating with an antireflection film, before engaging the first optical fiber 1 with the second optical fiber 2 by fusion or bonding.
  • the technical problem to be solved by the technical solution provided by the present invention is that when a light spot size of incident light is larger than the diameter of the fiber core of the optical fiber or the incident angle is larger than the numerical aperture angle of the optical fiber, a part of the incident light entering the cladding of the optical fiber damages the optical fiber due to the thermal effects, the principle of the structure of the input end of the optical fiber provided by Embodiment 1 will be explained below in two cases that the light spot size of the incident light is larger than the diameter of the fiber core of the optical fiber and the incident angle is larger than the numerical aperture angle of the optical fiber.
  • FIG. 4A is a schematic diagram showing an optical path in which the incident light enters the structure of the input end of the optical fiber according to one embodiment of the present invention.
  • FIG. 4A when the light spot size of the incident light is larger than the diameter ⁇ 2 of the fiber core of the first optical fiber 1 while the incident angle of the incident light meets the requirement of the numerical aperture angle of the optical fiber, marginal lights a, b of the incident light enter the first cladding of the first optical fiber and lights c, d of the incident light are coupled into the fiber core of the first optical fiber.
  • the diameter of the first cladding of the first optical fiber is larger than the diameter of the first cladding of the second optical fiber, after the lights a, b entering the first cladding of the first optical fiber transmit a certain distance in the first cladding of the first optical fiber, most of them leak into the outer space from the rear end of the first cladding of the first optical fiber; on the other hand, the lights c, d coupled into the fiber core of the first optical fiber, after transmitting to the engagement of the first optical fiber 1 and the second optical fiber 2 by repeated total reflections in the fiber core of the first optical fiber, because the diameter of the fiber core of the first optical fiber is smaller than or equal to that of the fiber core of the second optical fiber, are further coupled into the fiber core of the second optical fiber so as to form stable transmission.
  • FIG. 4B is a schematic diagram showing an optical path in which the incident light enters the structure of the input end of the optical fiber according to another embodiment of the present invention.
  • the incident angle ⁇ of the incident lights a′, b′ exceed the numerical aperture angle ⁇ of the first optical fiber 1 while the light spot size is smaller than the diameter ⁇ 2 of the fiber core of the first optical fiber 1
  • the incident lights a′, b′ after entering the fiber core of the first optical fiber, leak into the first cladding of the first optical fiber because of not meeting total reflection condition;
  • the incident lights c′, d′, the incident angle ⁇ of which meet the numerical aperture angle of the first optical fiber 1 are coupled into the fiber core of the first optical fiber.
  • the diameter of the first cladding of the first optical fiber is larger than the diameter of the first cladding of the second optical fiber, after the lights a′, b′ entering the first cladding of the first optical fiber transmit a certain distance in the first cladding of the first optical fiber, most of them leak into the outer space from the rear end of the first cladding of the first optical fiber rather than entering the second optical fiber 2 .
  • the incident lights c′, d′ the incident angle of which is equal to or smaller than the numerical aperture angle ⁇ of the first optical fiber 1 , will stably transmit in the fiber core of the first optical fiber, and after reaching the engagement of the first optical fiber 1 and the second optical fiber 2 , because the diameter of the fiber core of the first optical fiber is smaller than or equal to that of the fiber core of the second optical fiber, the incident lights c′, d′ will be further coupled into the fiber core of the second optical fiber so as to form stable transmission.
  • a length of the first optical fiber 1 having a cladding of a large diameter is engaged at the front end of the second optical fiber 2 so that most of the lights entering into the first cladding of the first optical fiber leak out from the rear end of the first cladding of the first optical fiber 1 , and only minor of them entering the first cladding of the second optical fiber from the rear end, which reduces the risk of the damage to the second optical fiber caused by the light in the cladding and improves the quality of the output light beam subjected to transmission in the optical fiber.
  • FIG. 5 is a schematic diagram showing a structure of an input end of the optical fiber according to Embodiment 2 of the present invention.
  • the structure of the input end of the optical fiber comprises a first optical fiber 1 and a second optical fiber 2 ; the first optical fiber 1 and the second optical fiber 2 are coaxial, one end of the first optical fiber 1 is used to receive optical beam, and the other end of the first optical fiber 1 is engaged with the second optical fiber.
  • the first optical fiber 1 comprises a fiber core, a first cladding surrounding the fiber core of the first optical fiber and a second cladding surrounding the first cladding of the first optical fiber;
  • the refractive index n of the fiber core of the first optical fiber, the refractive index n 1 of the first cladding of the first optical fiber and the refractive index n 2 of the second cladding of the first optical fiber can meet several relationships as follows: n 2 ⁇ n and n 1 ⁇ n, n>n 1 >n 2 , or n>n 2 >n 1 ;
  • the second optical fiber 2 comprises a fiber core and a first cladding surrounding the fiber core of the second optical fiber.
  • a diameter ⁇ 1 of the first cladding of the first optical fiber is larger than a diameter ⁇ 4 of the first cladding of the second optical fiber, and a difference between them is larger than a first preset threshold; the diameter ⁇ 2 of the fiber core of the first optical fiber is smaller than or equal to the diameter ⁇ 3 of the fiber core of the second optical fiber, and a difference between them is smaller than a second preset threshold.
  • both the first optical fiber 1 and the second optical fiber 2 are a multimode optical fiber, and the other end of the first optical fiber 1 is engaged with the second optical fiber 2 by way of electrode discharge fusion, laser heating fusion or adhesive bonding.
  • a ratio ⁇ 1 / ⁇ 2 of the diameter ⁇ 1 of the first cladding of the first optical fiber to the diameter ⁇ 2 of the fiber core of the first optical fiber is 1.1 ⁇ 50; the diameter ⁇ 2 of the fiber core of the first optical fiber is smaller than or equal to the diameter ⁇ 3 of the fiber core of the second optical fiber; the length L 1 of the first optical fiber 1 is 1 mm ⁇ 3000 mm.
  • the first optical fiber 1 can also be of a structure with multi-claddings, such as three-cladding structure, four-cladding structure and so on, the principle of which is the same as that of the above described double-cladding structure, which will not be repeated here.
  • the second optical fiber 2 can also be an optical fiber with multi-claddings.
  • the diameter of the first cladding of the first optical fiber should be larger than the diameter of the outermost cladding of the second optical fiber 2
  • the diameter of the fiber core of the first optical fiber should be smaller than or equal to the diameter of the fiber core of the second optical fiber.
  • FIG. 6 is a schematic diagram showing a structure of an input end of the optical fiber according to Embodiment 3 of the present invention.
  • the structure of the input end of the optical fiber comprises a first optical fiber 1 and a second optical fiber 2 ; the first optical fiber 1 and the second optical fiber 2 are coaxial, one end of the first optical fiber 1 is used to receive optical beam, and the other end of the first optical fiber 1 is engaged with the second optical fiber.
  • the first optical fiber 1 comprises a fiber core and a first cladding surrounding the fiber core of the first optical fiber;
  • the second optical fiber 2 comprises a fiber core and a first cladding surrounding the fiber core of the second optical fiber.
  • a diameter ⁇ 2 of the fiber core of the first optical fiber is smaller than or equal to a diameter ⁇ 3 of the fiber core of the second optical fiber, and a difference between them is smaller than a second preset threshold; in the axial direction of the first optical fiber 1 , a preset position is determined, for example, the axial distance from this preset position to one end of the first optical fiber 1 is equal to 3 ⁇ 4 of the length of the first optical fiber 1 , the diameter ⁇ 1 of the first cladding of the first optical fiber from the one end of the first optical fiber 1 to this preset position remains constant which is larger than the diameter ⁇ 4 of the first cladding of the second optical fiber, a difference of them is larger than a first preset threshold; the diameter of the first cladding of the first optical fiber
  • both the first optical fiber 1 and the second optical fiber 2 are a multimode optical fiber, and the other end of the first optical fiber 1 is engaged with the second optical fiber 2 by way of electrode discharge fusion, laser heating fusion or adhesive bonding.
  • a ratio ⁇ 1 / ⁇ 2 of the diameter ⁇ 1 of the first cladding of the first optical fiber to the diameter ⁇ 2 of the fiber core of the first optical fiber is 1.1 ⁇ 50; the diameter ⁇ 2 of the fiber core of the first optical fiber is smaller than or equal to the diameter ⁇ 3 of the fiber core of the second optical fiber; the length L 1 of the first optical fiber 1 is 1 mm ⁇ 3000 mm.
  • one end of the first cladding of the first optical fiber is processed into an inclined surface to make the leaked lights more divergent and reduce back reflection.
  • some transparent and non-absorbing glue can also be evenly placed at the engagement of the first optical fiber 1 and the second optical fiber 2 .
  • the glue at the interface shapes as conical. In this way, an inclined surface can also be formed at one end of the first optical fiber 1 , and it is easier to implement in processes relative to processing an inclined surface at the end of the optical fiber.
  • FIG. 7 is a schematic diagram showing a structure of an input end of the optical fiber according to Embodiment 4 of the present invention.
  • the structure of the input end of the optical fiber comprises a first optical fiber 1 , a second optical fiber 2 and an end cap 4 ; the first optical fiber 1 and the second optical fiber 2 are coaxial, one end of the end cap 4 is coated with an antireflection film, and the other end of the end cap 4 is engaged with one end of the first optical fiber 1 , and the other end of the first optical fiber 1 is engaged with the second optical fiber.
  • the first optical fiber 1 comprises a fiber core and a first cladding surrounding the fiber core of the first optical fiber;
  • the second optical fiber 2 comprises a fiber core and a first cladding surrounding the fiber core of the second optical fiber.
  • a material of the end cap 4 is quartz or glass, and a diameter of the end cap 4 is larger than a diameter ⁇ 2 of the fiber core of the first optical fiber, a diameter ⁇ 1 of the first cladding of the first optical fiber is larger than a diameter ⁇ 4 of the first cladding of the second optical fiber, and a difference between them is larger than a first preset threshold; the diameter ⁇ 2 of the fiber core of the first optical fiber is smaller than or equal to a diameter ⁇ 3 of the fiber core of the second optical fiber, and a difference between them is smaller than a second preset threshold.
  • both the first optical fiber 1 and the second optical fiber 2 are a multimode optical fiber, and the other end of the first optical fiber 1 is engaged with the second optical fiber 2 by way of electrode discharge fusion, laser heating fusion or adhesive bonding.
  • a ratio ⁇ 1 / ⁇ 2 of the diameter ⁇ 1 of the first cladding of the first optical fiber to the diameter ⁇ 2 of the fiber core of the first optical fiber is 1.1 ⁇ 50; the diameter ⁇ 2 of the fiber core of the first optical fiber is smaller than or equal to the diameter ⁇ 3 of the fiber core of the second optical fiber; a length L 1 of the first optical fiber 1 is 1 mm ⁇ 3000 mm.
  • the end cap 4 without any fiber core is added at the front end of the first optical fiber 1 , which helps to reduce the optical power density at the incident end and avoid the damage to the end face of the optical fiber when the incident laser is of high-power.
  • FIG. 8 is schematic diagram showing a structure of an input end of the optical fiber according to Embodiment 5 of the present invention.
  • the structure of the input end of the optical fiber comprises a first optical fiber 1 , a second optical fiber 2 and a sleeve 5 ; the first optical fiber 1 and the second optical fiber 2 are coaxial, one end of the first optical fiber 1 is used to receive optical beam, and the other end of the first optical fiber 1 is engaged with the second optical fiber; the sleeve 5 surrounds the first optical fiber 1 and the second optical fiber 2 .
  • the first optical fiber 1 comprises a fiber core and a first cladding surrounding the fiber core of the first optical fiber;
  • the second optical fiber 2 comprises a fiber core and a first cladding surrounding the fiber core of the second optical fiber.
  • a material of the sleeve 5 is metal or glass, and if the material of the sleeve 5 is metallic material such as copper, then it can also have an effect of heat dissipation;
  • a gap formed between the inner surface of the sleeve 5 and the outer surface of the first cladding of the second optical fiber is filled with glue or the sleeve 5 and the first cladding of the second optical fiber are welded together to protect and fix the second optical fiber 2 ;
  • the diameter ⁇ 1 of the first cladding of the first optical fiber is larger than the diameter ⁇ 4 of the first cladding of the second optical fiber, a difference of them is larger than a first preset threshold;
  • the diameter ⁇ 2 of the fiber core of the first optical fiber is smaller than or equal
  • both the first optical fiber 1 and the second optical fiber 2 are a multimode optical fiber, and the other end of the first optical fiber 1 is engaged with the second optical fiber 2 by way of electrode discharge fusion, laser heating fusion or adhesive bonding.
  • a ratio ⁇ 1 / ⁇ 2 of the diameter ⁇ 1 of the first cladding of the first optical fiber to the diameter ⁇ 2 of the fiber core of the first optical fiber is 1.1 ⁇ 50; the diameter ⁇ 2 of the fiber core of the first optical fiber is smaller than or equal to the diameter ⁇ 3 of the fiber core of the second optical fiber; and a length L 1 of the first optical fiber 1 is 1 mm ⁇ 3000 mm.
  • a length of optical fiber with a larger diameter is engaged at the front end of the optical fiber.
  • the structure of the input end of the optical fiber has advantages such as simple structure, easy for implementation, high reliability, and can efficiently prevent light from entering the cladding of the optical fiber so as to prevent light from converting into heat, thus avoiding the thermal damage to the optical fiber.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Couplings Of Light Guides (AREA)
US15/127,281 2015-12-08 2016-01-21 Structure of an input end of an optical fiber Active 2036-03-26 US9964706B2 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
CN201510900201.1A CN105403954A (zh) 2015-12-08 2015-12-08 一种光纤输入端结构
CN201510900201 2015-12-08
CN201510900201.1 2015-12-08
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